Heat exchange apparatus



June 11, 1968 K. w. STOOKEY HEAT EXCHANGE APPARATUS Filed Sept. 18, 1967 Atto neys Unite States Patent ABSTRAUT 9F THE DESCLGSURE An internally packed flexible joint disposed between the terminal wall blocks and tubes of a heat exchanger which is constructed of a sleeve having an outwardly annulus and packed with flexible and heat resisting fibers with spaced hangers for positioning the flexible joint between the top terminal wall blocks and tubes.

This is a continuation-in-part of Ser. No. 489,193, filed Sept. 22, 1965, now abandoned, for heat exchange apparatus.

This invention relates to a heat exchange apparatus and more particularly to a heat exchange apparatus known as a recuperator in the heavy metals industries. The invention is particularly adapted for use in recovering a part of the residual heat from the flow of blast furnace gases which are exhausted to atmosphere during blast furnace operation but which before being exhausted are passed through a heat exchanger to preheat incoming air which is then used for blast furnace operation. These are the uses which prompted the present invention but by mention of this, I do not intend to limit the invention to this particular application.

In order for a recuperator to function satisfactorily, the two gases which are passed in heat exchange relation must be adequately sealed apart; if the two flows are allowed to intermix, there will result a contamination of one of the flows and also produce a pressure drop which proportionately decreases the rate of circulation of the gases.

1 have disclosed in my previous filed and copending application, Ser. No. 215,846, filed Aug. 9, 1962, titled Refractory Heat Exchanger, now Patent No. 3,220,713, an improvement in the art of heat exchange, i.e., recuperators, which is significant in the art because it incorporates almost entirely ceramic components which are heat resistant and are thereby capable of operation with gases at substantially higher temperatures than previously could be withstood. At the same time, the refractory members are prone to crack during heat-up and cool-down if the parts are locked together. Consequently, my approach has been to provide for free floating of the recuperator components to prevent soil damage during heat-up and cooldown periods. These novel results are attained by using novel head wall constructions which tend to maintain the various seals within the recuperator, while at the same time permitting slight relative movements which inevitably occur because of the unequal distribution of heat on various components of the recuperator.

In a recuperator of the type described, it has been found that slight leakage flows tend to occur between the wall openings on the ends of the conduits which register with openings in the head blocks and this is particularly prone to occur if the head blocks tend to hold together and the end of the conduit shrinks away from registry with the opening in said head block. Thus gas flows witl in the conduits and gas flows within the recuperator chamber and there is a heat exchanging operation, but such operation is impaired by the occurrence of these leakage paths. The head walls, conduits and seals are all of heatresistant composition. As a further consequence of the:

leakage paths between the openings in the head walls and the registered openings in the conduits, there is in addition to the loss of efiiciency in operation of the recuperator, an undesirable mixing of the flows which make up the two gases exchanging heat.

Accordingly, it is a principal object of the present invention to provide an improved rccuperator operation, in a recuperator of the refractory class described, which is sealed and remains sealed while permitting relative expansion and contraction of the component parts.

It is a further object of the invention to provide an improved sealing arrangement for the recuperator which increases the efficiency in operation of the recuperator and completely separates the two flows which are passed in heat exchanging relation.

It is one of the over-all objects of the present invention to produce a recuperator which is adequately sealed and with a sealing means which permits inevitable relative movements of the recuperator parts, is inexpensive to construct, to install, and to service.

A salient feature of the invention is to provide spaced hangers for maintaining the flexible joint in a predetermined position with respect to the head block and sleeve.

Summary With an increase of pressure differentials and an increase in tube length of a heat exchanger, leakage can be severe between the top terminal wall blocks and tubes. An internally packed flexible joint between the terminal wall blocks and tubes constructed of a sleeve having an outwardly annulus and packed with flexible and heat resisting fiber and held in a predetermined position by spaced hangers will preclude leakage between the terminal wall blocks and tubes.

Further objects and features of the invention will become apparent from a consideration of the description, which proceeds with reference to the accompanying drawings, wherein:

FlGURE 1 is a section view taken through the middle of the recuperator and illustrating one of the refractory tubes and core busters in longitudinal section and further illustrating the flow paths of the gases;

FIGURE 2 is a top view of the seal in the upper portion of the head wall and tube and taken on line 22 of FIGURE 3; and,

FIGURE 3 is an enlarged sectional view of the structure shown in FIGURE 2 and looking in the direction of the arrows 33 in FIGURE 2.

Referring now to the drawings, the heat exchanger designated generally by reference numeral 10 is of the character and structure designated in the aforementioned patent application Ser. No. 215,846, now Patent No. 3,220,713. In brief review, however, the heat exchanger includes a chamber constructed of fire brick 11 which is of suitable heat-resistant composition, and surrounded by a castable ceramic liner 13 and metal shell 15. The fire brick is used to make up the vertical walls and the upper and lower horizontal walls are made up of refractory head blocks 2%. Over the upper head wall blocks are stacks of additional blocks 18, these walls and head blocks (upper and lower) define an internal chamber 22 which receives a first flow of gas originating from inlet 24 and passing in the direction of the full line arrows 26 into a compartment 28. From the compartment 23 the flow is directed upwardly through openings 30 in a series of mating blocks 32 which are supported on pedestals 33 and are sealed in their peripheries with suitable sealing material 34, the composition of which is fully described and discussed in patent application Ser. No. 215,846, now Patent No. 3,220,713.

The flow is then directed upwardly by a series of vertically stacked sleeves 36 which surround tubes 38 leaving a slight annular space 37 which channels the flow upwardly until it emerges at the top of the uppermost sleeve and passes into chamber 22, as indicated by the full line arrows. The flow is then collected within chamber 22 and emerges through outlet 42. Because of the narrow space 37 between the sleeve and the tube there is a fast rate of linear flow which improves the heat exchange coefficient and the entire tube is swept from one end to the other, the tube thereby being subjected to maximum heat exchange with the gas flow which occurs interiorly of the tube and which will now be discussed. The composition of the tube is of a suitable heat-resistant material construction, such as silicon carbide and will resist cracking or fracturing during heat-up and cooling-down periods.

The ends of the tubes are not positively connected to the head walls 18 and 20, but individually bear against companion head blocks at their opposite ends, each conduit having a separate head block. The head blocks are normally free to float, one with respect to the other, to expand or contract at a different rate than the adjacent head block and conduit. The head blocks can be prevented from such relative movement when the sealing material between adjacent head blocks is packed so tightly as to prevent this movement. The packing of refractory material is designated by reference numeral 44 and is of flexible and heat-resisting fibers. When these fibers are tightly compacted, the head blocks tend to adhere more rigidly together and during cooling there is a tendency for the end of the tube or conduit to shrink away from sealing engagement with the head block.

Where the ends of the conduits 38 engage the head blocks 20, there is a tapered seat 46 (FIGURE 3) and this particular connection, being an impositive connection, permits relative movements between the head blocks 20 and the end of the conduits 38 which are prone to develop leakage paths for the gas flow indicated by wavy line arrows 50 passing through aligned openings in the head blocks and superimposed refractory blocks 52. The flow indicated by arrows 5t} originates from an inlet 54 and after passing into chamber 56 is directed downwardly through openings 69 and into the tubes 38 where the flow is directed downwardly as indicated by arrow 66. The flow is subdivided into quadrants by a core buster 68 which subdivides the flow, insuring better distribution of heat and flow and improving the mechanism of heat exchange across the thickness of the wall between the countercurrent flows of gases within the annular space 37 and interiorly of the tube 36 respectively.

The juncture between the ends of the tubes or conduits 38 and the head blocks 20 are sealed by sleeve 71 of refractory or metallic composition depending upon the operating temperature of the gases and is mounted inside the opening in the wall block. The sleeve 71 extends into the interior of the tube or conduit 38 (FIGURE 3) the bottom 70 of the sleeve being flared to produce an annulus 73 to retain a heat-resistant packing 72, which seats within the space between the sleeve and the confronting surfaces of the head block and tube. The space can vary but it is approximately /2 inch and the packing is of flexible heat-resistant material. The sleeve 71 can vary in length, but is generally about 6 to 8 inches long and is divided evenly on each side of the juncture of the head block and flue-tube end. A number of spaced hanger members 91 having an outwardly directed flange 93 at its lower end for supporting and positioning the sleeve 71 in a predetermined position is disposed in each opening 60. The hanger 91 is provided with an outwardly directed flange 95 at its upper end, which flange is adapted to rest on top of the head block 20 (FIGURE 3). The hanger members 91 are spaced from each other by a cross member 97. If desired, more than two hangers can be used in which event the hangers are spaced from each other by a web (not shown) in place of the cross members 97. Should the head block tend to shrink away from the flue-tube 38 end (or vice versa) the combination sleeve and packing forms a flexible joint which will prevent leakage across the joined. part of the flue-tube and head block. It has been found in actual practice that the resilient packing 72 I has a tendency to lose its resilience whereby the sleeve 71 When there is a high pressure differential between the two gas flows, the leakage is considerable should there occur tube end separation. By reason, however, of the combination sleeve 71 and packing 72, the seal is maintained even though there is a slight clearance which develops between the end of the tube and its companion sealing surface of the head block (FIGURE 3). In other words, what develops is a slip joint which precludes leakage.

While the sleeve can vary in its composition, it is us ually of silicon carbide or aluminum-silica, or metallic composition, or other refractory material and the packing is similarly of a heat-resistant material and most often is a fibrous aluminum-silica material. In constructing the heat exchanger, the conduits 38 may be of silicon carbide or other heat-resistant material and vary in length from about 2 /2 feet to as high as 10l5 feet long. The functional requirements of the material is that it is impervious to the gases and is of a suitable conductivity in order to transmit heat between the interior and exterior flows of gases.

There is no criticality in the direction or passage of flows, the cooler air can flow either within the tube or outside the tube, all that is required is that the two flows be separated. Also, the flows can be recirculated to make one or more passes depending on design considerations. Typically, however, the hot gases are circulated over the outside of the tubes and the cooler or heat-receiving flow of gases is circulated through the interior of conduit only once. Thus, the hot gas flow of furnace gas is introduced from inlet 24 to chamber 28 and is passed upwardly through openings 30 and into the annular space 37 be tween the stack of sleeves 36 and tube 38, emerging from the top of the uppermost sleeve and entering chamber 22, all of the flows being collected in chamber 22 and exited through passage 42. The upwardly flowing hot gases sweep the external surface of the tube 38 and etfect heat exchange with the cooler countercurrently flowing cool air which passes downwardly within the conduit as indicated by the arrows 66.

Cool air originates from inlet-54 leading to chamber 56 and is directed downwardly through opening 60 of the stacked blocks 52. These openings 60 register with the inlet opening of the conduit or tube. The heated air passes through the conduit, then passes through registered openings in the lower head blocks and into a chamber 74 where all of the flows from the tubes 38 are combined and are discharged as indicated by arrow 50. Should there occur a bridging between the upper head blocks, and a contraction of tubes '38, leakage paths will not develop which will allow a mixing of the air and heated gas. In-

stead, the air is guided past any gaps between the conduit end and head blocks by the sleeve 71 and packing 72 which maintain a slip joint seal at the juncture of the upper end of the tube and its companion head block opening.

Although the invention has been illustrated and described in a single embodiment, it will be understood that the single embodiment is illustrative of the invention and is by no means restrictive thereof. It is reasonable to be expected that those skilled in this art can make m1- merous revisions and adaptations of the invention to suit design requirements, and it is intended that such revisions and adaptations will be included within the scope of the following claims as equivalents of the invention.

I claim:

1. In a heat exchanger the combination of two spaced head walls disposed at the upper and lower ends of the heat exchanger chamber, means forming an inlet and an outlet for the circulation of gases through said heat exchanger cnamber, aligned pairs of openings in said head walls, vertically disposed tubes which are mounted, one between each of said vertically aligned pairs of the openings, to receive a flow of gases therethrough and thereby effect -a heat exchange through the heat conductive walls of said tubes with the gases circulating exteriorly of said tubes and Within said heat exchanger chamber, the improvement comprising, means for sealing the juncture between the aligned pair of openings in the tubes and head blocks including a sleeve of heat resistance composition which telescope within the interior of the tube and the opening in the head block, a packing of heat-resistant material surrounding each sleeve, and supporting means for retaining said sleeve in a predetermined position within the opening of said head block.

2. A heat exchanger in accordance with claim 1, wherein the supporting means includes a member having an outwardly directed flange at each end, said member being disposed within the opening in the head block and sleeve, said member positioned so that one flange rests on top of said head block and the other flange disposed below and in contact with said sleeve to prevent the sleeve from sliding out of position.

3. A heat exchanger in accordance with claim 1, wherein the supporting means includes a hanger having a number of members spaced apart and each member having an upper outwardly directed flange for supporting said hanger within the opening of said head block and a lower outwardly directed flange in contact with the lower end of the sleeve to prevent the sleeve from sliding out of position.

4. A heat exchanger in accordance with claim 1, wherein the packing of heat-resistant material which surrounds said sleeve is constructed of a refractory composition.

5. A heat exchanger in accordance with claim 1, wherein said sleeve is provided with an outwardly directed annulus to retain said packing between the sleeve, head wall and tube.

6. A heat exchanger in accordance with claim 1, wherein an insert is dispose-d within said tube to divide the flow of gases thereof into a plurality of distinct flow paths as the gases move longitudinally therein.

7. A heat exchanger in accordance with claim 1, wherein said sleeve is constructed of a refractory composition.

8. In a heat exchanger the combination of two space-d head walls at the upper and lower ends of the heat exchanger chamber, means forming an inlet and an outlet for the circulation of gases through said heat exchanger chamber, aligned pairs of openings in said head Walls, vertically disposed tubes which are mounted, one between each of said vertically aligned pairs of the openings, to receive a flow of gases therethrough and thereby effect a heat exchange through the heat conductive walls of said tubes with the gases circulating exteriorly of said tubes and within said heat exchanger chamber, the improvement comprising means for sealing the juncture between the aligned pairs of openings in the tubes and head block-s including sleeves of refractory composition which telescope within the interior of the tubes and the openings in the head blocks to cover the said junctures, and a packing of heat-resistant refractory material surrounding each sleeve, said sleeves having an outwardly directed annulus to retain said packing between the sleeve, head wall, and tube, and means surrounding said tubes to define an annular passage closely adjacent the tube for the fiow of gases within said chamber in 'heat exchanging relation with the gas flow interiorly of said conduits, said flow Within said conduit and within said annular space being in countercurrent relation.

References Cited UNITED STATES PATENTS 1,782,430 11/1930 Kelley et al. 26320 3,129,931 4/1964 Stockey -n 263-20 3,220,713 11/1965 Stookey 263-20 JOHN J. CAMBY, Acting Primary Examiner. 

